9Liにおける非軸対称変形の効果(I)

RCNP研究会「核子・ハイペロン多体系におけるクラスター現象」
(7月26,27日, 2013 at関東学院大学KGU関内メディアセンター)
微視的核構造反応模型を用いた
9Li 原子核の励起状態の研究
古本猛憲
(一関工業高等専門学校)
共同研究者
須原唯広 (松江工業高等専門学校)
板垣直之 (京都大学基礎物理学研究所)
Contents
• Motivation
- The 9Li nucleus has a role of the core in 11Li
- Structures of the 9Li nucleus
• Formalism
- Stochastic Multi-configuration mixing Method
- Microscopic Coupled Channel (MCC) Method
with complex G-matrix interaction (CEG07)
• Results
- Elastic & Inelastic cross sections
- Discussion for the second 3/2- state
• Summary
Motivation
7Be
Halo structure
+p
Z=5
8B
Z=4
7Be
Z=3
6Li
Z=2
4He
N=2
9B
10B
9Be
7Li
8Li
6He
N=3
N=4
11B
12B
10Be 11Be
9Li
13B
+ nN=6
+n
+n
12Be
11Li
8He
4N=5
He
10Be
9Li
N=7
+n+n
N=8
Experiment
I. Tanihata et. al., (Phys. Rev. Lett. 55 (1985) 2676)
T. Minamisono et. al., (Phys. Rev. Lett. 69 (1992) 2058)
I. Tanihata, (J. Phys. G: Nucl. Part. Phys. 22 (1996) 157)
Motivation
Break up of 11Be → 10Be + n
Importance role of the core excitation
for the nuclear reaction
8B
elastic scattering
11Li
9Li
has a halo structure
itself in this study
K. Horii et. al., (Phys. Rev. C.81 (2010) 061602(R))
A. M. Moro et. al., (Phys. Rev. C.85 (2012) 054613)
9Li
Formalism (Structure)
α
Brink model + Stochastic multi-configuration mixing

J M
  ci , K i
K
i
J  MK
n1
Z
t
n2
J  MK
Randomly fixed
i
 P  P JMK [ A{ (r1r2r3r4 , R1 )t (r5r6r7 , R 2 )n1 (r8 , R 3 )n2 (r9 , R 4 )}]
2
 
Rk  
 (r j , R k )  exp  r j 
  j
  
 
Hamiltonian
Effective NN interaction

 2  1.46


 j : spin and isospin parts
A
A
i 1
i j
Hˆ   tˆi  Tˆc.m.   vˆij
Central : Volkov No.2 (W=1-M, M=0.6, B=H=0.08)
LS
: G3RS
(VLS=2000MeV)
Energies & rms radii
& B(E2)
[7] No-core
shell model
B(E2; 1/2- → 3/2-)
Exp. 6.8(3) e2fm4
Cal. 8.778 e2fm4
[8] TOSM + UCOM
[9] α + t + n + n
[11] 6He + t
T. Furumoto, T. Suhara, and N. Itagaki (Phys. Rev. C.87 (2013) 064320)
Formalism (Reaction)
Microscopic Coupled Channel (MCC)
N
 TR  U (R)  E   (R)   U (R)   (R)
 
The diagonal and coupling potentials are derived from microscopic
view point.
U  (R )   
( P)
ik
(r1 ) 
(T )
jl
(r2 )v NN (s;ρ, E )dr1dr2
transition density
CEG07
vNN(s)
Transition density
 ik(r)   i( )  (r i r)  k ( )
r2
r1
R
i
Projectile
Target
Quasi-elastic 9Li + 12C cross section
In MCC with CEG07
U  V  iW
U  V  iNW W
to reproduce the data
T. Furumoto, T. Suhara, and N. Itagaki (Phys. Rev. C.87 (2013) 064320)
Elastic & Inelastic
cross sections
T. Furumoto, T. Suhara, and N. Itagaki
(Phys. Rev. C.87 (2013) 064320)
Decomposition into monopole & quadrupole
transitions
Monopole
Quadrupole
T. Furumoto, T. Suhara, and N. Itagaki
(Phys. Rev. C.87 (2013) 064320)
Mutual-excitation and multistep effects
✔Mutual-excitation (12C*) effect
Minor role for all 3/2- states
✔Multistep (9Li*) effect
Drastic change of the 3/22- state
Minor role for other 3/2- states
T. Furumoto, T. Suhara, and N. Itagaki
(Phys. Rev. C.87 (2013) 064320)
Second 3/2- state shows exotic behavior
in the inelastic angular distribution
Need for the investigation of the state in detail
Decomposition into K-quantum number
9Li
n1
α
K = 1/2 only
K = 3/2 only

J M
Z
t
n2
  ci , K 
J  MK
i
K
i
T. Furumoto, T. Suhara, and N. Itagaki
(Phys. Rev. C.87 (2013) 064320)
Deformation of 9Li
Exp. -2.53(9) efm2
In the collective model
3K 2  J ( J  1)
QJ 
Q0
2 J ( J  1)
K = 1/2 only
K = 3/2 only
T. Furumoto, T. Suhara, and N. Itagaki
(Phys. Rev. C.87 (2013) 064320)
In the assumption,
all Q0 gives positive values
Prolate like deformation
Behavior of two valence neutrons in 9Li
α + t + di-neutron
α + α + di-neutron
T. Furumoto, T. Suhara, and N. Itagaki
(Phys. Rev. C.87 (2013) 064320)
10Be
n
α
9Li
α
n
Analogy
n
α
t
n
Multi-step effect
T. Furumoto, T. Suhara, and N. Itagaki
(Phys. Rev. C.87 (2013) 064320)
Summary
• Application of microscopic cluster and microscopic
folding modes to 9Li nuclear scatterings
• Inelastic cross section to the 3/2- state
- Quadrupole transition for the 2nd 3/2- state
- Monopole transition for the 3rd and 4th 3/2- states
• Possibility in the 2nd 3/2- state
- triaxial deformation & mixing of di-neutron components
• The multi-step coupling effect
- important for the 2nd 3/2- state
- through the 1st 1/2- and 5/2- states

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